Nalbuphine hydrochloride, also known as 4((−)-17-(cyclobutylmethyl)-4,5α-epoxymorphinan-3,6α,14-triol hydrochloride, (C21H28ClNO4, MW 393.90) is a synthetic opioid agonist-antagonist analgesic of the phenanthrene series. The chemical structure of nalbuphine hydrochloride is shown below

Nalbuphine HCl is structurally related to both the widely used opioid antagonist, naloxone, and the potent opioid analgesic, oxymorphone. Nalbuphine hydrochloride is an effective analgesic indicated for the relief of moderate to severe pain. Nalbuphine hydrochloride may also be used as a supplement to balanced anesthesia, for preoperative and postoperative analgesia, and for obstetrical analgesia during labor and delivery. Nalbuphine hydrochloride is commercially available as an injectable solution in two concentrations, more particularly in 10 mg and 20 mg of nalbuphine hydrochloride per mL.